Lactarane

Successful resolutions of hydrogenated naphthalenes by acylation in organic solvent have been described. Thus, CALB (Novozym 435) catalyzes the acylation with vinyl acetate at 40 °C in hexane of three cis-fused octahydronaphthalenols to furnish after 48 h the acetylated products 72-74 and the remaining alcohol in high ees and with excellent E (Scheme 4.27, products 72-74 shown) [88]. Similarly, a key intermediate in the synthesis of natural products of the marasmane and lactarane... 

Wunder A, Anke T, Klostermeyer D, Steglich W (1996) Lactarane Type Sesquiterpenoids as Inhibitors of Leukotriene Biosynthesis and Other, New Metabolites from Submerged Cultures of Lentinellus cochleatus (Pers. ex Fr.) Karst. Z Naturforsch 51c 493... 

Drimane, farnesane, glutinopallane, protoilludane, isolactarane, and guaiane sesquiterpenes have been isolated so far in a few Lactarius species therefore, they may be considered chemotaxonomic markers. By contrast, large quantities of marasmane, lactarane and secolactarane metabolites occur in almost all Sections, as reported in Table 24. 

The carbons 5 and 13 of the skeletons of many marasmane, lactarane and secolactarane... 

New sesquiterpenes of the lactarane (occasionally named also vellerane) group (Table 10) have been isolated by Swedish authors during their pioneering work on the chemical defence system of Lactarius species. Vellerol (10.8) and vellerdiol (10.20) were first isolated from extracts of Lactarius vellereus made at different times after grinding the mushrooms (27). The reduction of either... 

Recently, several papers have reported the isolation of new lactarane lactones, possessing the methyl group at C-3 either cis or trans to H-2, and the lactone carbonyl group either at C-5 (5-lactaranolides. Tables 11-13) or at C-13 (13-lactaranolides, Tables 16-17). Differentiation between these structural alternatives on the basis of spectroscopic data alone has been often risky, especially when only a single isomer is at hand. Therefore, chemical correlations, synthesis of the possible isomers, and molecular mechanics calculations have always been performed in order to corroborate spectroscopic informations. 

Expulsion of the C-8 carbonyl group from the lactarane skeleton of compound 1U3 has been suggested to occur via a benzylic-Iike rearrangement, followed by a decarboxylative aromatization (70) (Scheme 9). 

Furantriol (18.27), isolated from L. mitissimus (84), is one of the few lactarane sesquiterpenes in which one of the gem-methyl groups at C-11 is oxidized and it was chemically correlated (82) with lactarorufin B (11.71), another example of this kind. The Polish authors suggested that lactone 11.71 was enzymatically formed from furan 18.27, and that a C-15 oxidized sesquiterpene of the velutinal type was the common precursor of both compounds in the mushroom (84). Actually, the possibility for the C-15 methyl group to be oxidized at an early stage of the lactarane biosynthesis seems to be confirmed by the recent finding of C-15 hydroxylated protoilludane sesquiterpenoids (5.1 and 5.2) in L. violascens (23) (Table 5). 

Noteworthy among these conversions are the first successful cyclizations of lactone and furan secolactaranes to the corresponding lactarane sesquiterpenes, which were obtained by a Me2AlCl catalysed ene reaction (60). Under these conditions lactaral (19.1) yielded directly the diene 18.1, identical with the dehydration product of furosardonin A (18.8), while smooth cyclization of aldehyde 14.3 gave the lactone 11.8 in which the protons H-8 and H-9 have the "unnatural" cis stereochemistry. This result could be anticipated by examination of the Dreiding models of the two possible transition states 11.8 A and 11.8 B, which showed that unfavourable steric interactions developing between the C-3 methyl group and the bulky >C=0-—AI J complex are minimized in the... 

Flavidulol D was isolated from L. flavidulus, and its structure was identified as the stearate of flavidulol A (22.8) on the basis of spectroscopic data (147). The new marasmane lactone P3 and diketopiperazine P4 were isolated from the most polar fraction of an ethanolic extract of L. vellereus (148). The structures of compounds P3 and P4 were established by extensive NMR studies together with acetylation reactions. The isolation of lactone P3 suggested that the possible oxidation of the 15-methyl group, typical of a few lactarane sesquiterpenes, could take place at the early velutinal stage... 

The total synthesis of (+)-furoscrobiculin B, a lactarane sesquiterpene isolated from basidiomycetes of mushrooms, was accomplished in the laboratory of H. Suemune and K. Kanematsu using a furan ring transfer reaction and a semipinacol rearrangement as key steps. The secondary hydroxyl group of the tricyclic c/s-vicinal diol substrate was converted to the corresponding tosylate that in situ underwent a ring-expansion reaction to afford an azulenofuran in good yield. 

A number of new lactarane sesquiterpenoids have been identified from Lactarius scrobiculatus these include furoscrobiculin A (397), furanether A (398), furanether... 

The quaking aspen tree (Populus tremuloides) is a common tree in North America that is used for its timber. The wood-rotting pathogen Phellinus tre-mulae causes significant economic losses of this tree. Although the sesqui-terpenoid metabolites such as tremulenolide A (5.89) have a carbon skeleton that is isomeric with the lactaranes, some doubts have been expressed on its biosynthetic origin from farnesyl diphosphate. 

Basidiomycetes). L. is formed, like lactaral C HjOj, Mr 232.32, oil, [a]c -7.6° (CHCI3) and other secolac-taranes, in the fungi by enzymatic and chemical transformations from marasmane and lactarane precursors. 

Sesquiterpenes (sesquiterpenoids). A structurally highly diverse class of terpenoids with 15 carbon atoms skeleton derived biosynthetically from famesyl pyrophosphate (FPP) ( famesol, isoprene rule, ter-penes). More than 70 different ring systems are formed by enzyme-catalyzed cyclization of the linear parent structure these cyclic structures can be further modified by 1,2- and 1,3-hydride shifts, renewed cycliza-tions, hydroxylations, and other subsequent reactions. S. are widely distributed in plants, fiingi, and animals but are less common in bacteria. Specific biosynthetic routes are often characteristic for certain organisms. Thus, basidiomycetes preferentially use humulene as the basis for the syntheses of protoilludanes, illu-danes, lactaranes, hirsutanes, and related S. skeletons. Individual S. systems are also known for liverworts and marine organisms. In addition, liverworts often contain the optical antipodes of S. known from plants. 

C15H20O2. Mr 232.32, cryst., mp. 86.5-87.5°C, [a]o -25° (CHClj). A lactarane derivative with a pungent taste and mutagenic and antimicrobial activities from toadstools of the genera Lactarius (milk caps). Russula, and other Russulaceae like the isomeric isovel-leral V. is formed enzymatically from stearoylveluti-nal within a few seconds after injury of the fruit body. This is followed in fungi such as L vellereus by an enzymatic detoxification in which V. is reduced within a few minutes to vellerol (C,5H2202, Mr 234.34). Vel-leral and isovelleral have antifeedant effects on insects and mammals (opossum). 

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